Safety apparatus for heating inflammable liquids by conduction at nonigniting temperatures



y 1942- A. L. TANNEHILL 2,291,421 SAFETY APPARATUS FDR HEATINGINFLAMMABLIE LIQUIDS BY CONDUCTION AT :IONIGNITING TEMPERATURES FileJune 27, 1941 laweniarx L. 73/V/VEH/L L Patented July 28, 1942 SAFETYAPPARATUS ,FOR HEATING IN- FLAMDIABLE LIQUIDS BY CONDUCTION- ATNONIGNITING TEMPERATURES Arthur L. Tannehill, Gary, Ind.

Application June 27, 1941, Serial No. 400,142

4 Claims.

This invention relates to an apparatus for heating, boiling, evaporatingor distilling liquids, and more especially for distilling volatileinflammable liquids.

One object of the invention is to provide a means whereby the risk offlre attendant on heating, evaporating or distilling inflammable liquidsis avoided. As an illustrative example of the application of the methodand apparatus, it-

may be used in making distillation tests on inflammable liquids, such asgasoline and benzol, without risk of fire.

The distillation test is generally made in a manner similar to themethod of the American Society Testing Materials designation D 86--35,described in part II, page 870, American Society Testing MaterialsStandardsl936. This method involves boiling a sample of 100 millilitersof the inflammable liquid in a spherical glass flask over an open flameor over an electrical heating element which is of sufliciently hightemperature'to ignite or kindle the vapors. In case of a spill of theliquid through breakage of the flask, or other reason, the personconducting the test is in serious danger. Fatal accidents have resultedfrom this method of testing. It is highly desirable, therefore, toemploy a means and method of heating which will minimize or eliminatethis hazard.

When making the test in accordance with the prior art teaching, thespherical flask is placed on an asbestos board having a round hole about1 A" indiameter, into which the flask is fitted. The flame or othersource of heat is placed htlow the board, and only a small portion ofthe area of the flask at the bottom isexposed to the heat. The purposeof this arrangement is to avoid superheating the vapors of the boilingliquid. Since the direct heating area is restricted, the rate ofdistillation prescribed has necessitated a high temperature source ofheat, whether the heat was supplied through convection by the hot gasesfrom a flame or through the radiation of an electrically heated coil.

The apparatus and method of my invention supplies the heat at a sumcientrate primarily have been flat throughout. Such plates are not suitablefor the purpose of making distillation tests, because the area ofcontact between a spherical flask and a fiat heating plate isexcessively small, and a suiflcient amount and rate of heat transfer toeffect the required distilling rate, in these prior art devices, cannotbe obtained when the flat plate is at a temperature below the ignitiontemperature.

I have found that by making the heating plate of a dished or concaveform-so that a sumcient area of the heating plate conforms to the outerconvex contour of the flask, heat is uniformly transferred by conductiononly, directly to the flask at any desired rate over a well-definedarea, while maintaining the temperature of the conductive heating plateand all exposed parts of the apparatus, below the ignition or kindlingtemperature of the inflammable liquid. The fire or explosion hazard istherefore eliminated. I have also found that any prescribed distillationrate can be uniformly maintained, with more ease and certainty than byany other means of heating. I have further found that the superheatingof the vapors can be avoided by control of the area, by restricting thediameter of the dished portion of the plate which is in heat conduotiverelation with the flask, and by screen ing that portion of the flaskabove and out of direct heat conductive relation with the heating plate,from the radiant heat or heat by conduction from other portions of thehotplate not in direct heat conductive relation with the flask. Asuitable apparatus for the practice of the method of m invention mightbe constructed in a number of ways and of various materials. Anapparatus and method which I have found highly satisfactory isillustrated in the drawing.

Referring to the drawing, a dished or concave seat 6 is provided on theraised portion 5 of the hot plate Ll on which the flask l rests. Thelower portion of the flask l is of a general spherical form. For use onbenzol, toluol, xylol, etc. (the chemical names used to designatecorresponding pure compounds are benzene, toluene, xylene, etc), thedished or concave portion ti of the hot plate is 1 inches in diameterand the radius of curvature of the dished or concaved recess ii is 1inches, which is the same as the convex seat of the flask 9, since theflask is 3 inches in diameter. The lower body portion of the hot platedis 4 inches in diameter and inch thick at the sides. The raised portion5 in the center of the hot plate 3, which carries the dish-like orconcave seat t, extends A;

conductive contact relation to the flask. said area of an area in excessof the largest horizontal of conductive contact relation depending uponsection of the flask, the seat-to-base area ratio the particular liquidand the rate of volatilizabeing not less than 1 to 4 for brass, and heattion and distillation desired, the temperature of insulating meansinterposed between the consaid conductive medium at the seat being below5 ductive medium and the flask excepting at the the ignition point ofthe volatile gases, said heat seat area where the flask is in heatconductive conductive medium having a base area substancontact relationwith the heat conductive metially larger than said seat area on theupper dium, whereby the volatile gases in the flask are side and beingcomposed of brass or other meprote t d rom b i sup rh at d and accidiumhaving a heat conductivity of from about 10 dental contact by anyspilled liquid with a heat- 0.1 to 0.25. ing source at a temperature ator above the 4. Safety and non-superheating distilling a flash orignition p0 t of the liquid is precluded paratus as defined in claim 3,said base being ARTH L. TANNEHILL.

